CN100429781C - Electroluminescent panels with light extraction elements - Google Patents

Abstract

Each optical light extraction element (20, 30) comprises: an input interface (21, 31) which is optically coupled with the emissive surface of the cells or that of the substrate of the panel in such a way as to capture the rays emitted by said cells, an output interface (23, 33) having a suitable shape such that the rays emitted by the cells pass therethrough, and, optionally, a reflecting surface (32) which modifies the path of said rays such as to reduce the incidence angle with the aforementioned output interface. In this way, the light emitting efficiency of the panel is significantly improved.

Description

Electroluminescent panels with light extraction elements

technical field

The present invention relates to a luminescent or image display panel comprising a one- or two-dimensional matrix of organic light-emitting cells (or OLEDs), with means making it easy to extract the light emitted by these cells, which means greatly improving the luminous efficiency.

Background technique

Such a board typically consists of a substrate supporting a thin organic electroluminescent layer interposed between two electrode arrays, one of which is an array of anodes and the other an array of cathodes for powering the cells ; each cell is located in the overlapping area between an anode and a cathode; in the case of a passive matrix panel, each array is usually formed by electrodes in the form of parallel strips of constant width; the electrodes of the anode array are usually perpendicular to the electrodes of the cathode array; For multicolor display panels, especially for three-color display panels, the organic electroluminescent layer is usually divided into alternating bands of different emitting colors.

In the case of an active matrix board, the substrate contains the electronic components for the drive unit, in the case of a passive matrix board the substrate is usually made of glass or plastic; the thickness of the substrate is usually between 300 μm and 1500 μm , that is, 500 to 100 times larger than the thickness of the unit; the size or diameter of the unit or pixel is usually between 100 μm and 300 μm, that is, 1 to 15 times smaller than the thickness of the substrate; The electrode layer interposed between the substrate and the electroluminescent layer is coated before the luminescent layer and is therefore often referred to as the "lower layer"; another electrode layer applied after the electroluminescent layer is referred to as the "upper layer" ; the strip of the upper electrode layer is parallel to the electroluminescent layer it at least partially covers and is located in the center of the electroluminescent layer.

Depending on the circumstances, the light emitted by the panel must pass through the substrate in order for the image to be displayed to reach the viewer (in the case of a "back-lit" panel), or it does not have to pass through the substrate so that it reaches the observer (in the case of a "top-lit" panel). in the case of "glow" boards).

Typically, the light emitted by the panel must pass through an array of electrodes, either the lower layer (in the case of a back-emitting panel) or the upper layer (in the case of a top-emitting panel), before passing through the exit face of the panel where it enters the air in the direction of the observer. case); the other layer is then usually reflective in order to recover light exiting the cell in the opposite direction to the observer and redirect it through the exit face of the plate towards the outside of the plate.

Thus, one of the electrode layers is usually transparent, for example based on ITO, in order to serve as an anode, while the other is preferably made of a light-absorbing or even light-reflecting metal.

The large refractive index difference between the electroluminescent layer and air greatly limits the level of light extraction; this is because within the panel, total reflections reach the emissive layer at angles of incidence greater than the critical angle of refraction (or total reflection angle). Any light at the interface with air is generally lost.

In order to limit this loss, references JP10-223367, WO 01/33598 equivalent to US2002-0118271, and JP11-354271 show how to coat the exit face of an OLED type plate with a lens array for light extraction Inspiration:

- One ball lens per cell, or one cylindrical lens per row of cells;

- or multiple microlenses per unit.

The light extraction systems described in these references are based on the refraction of light at the exit of the cell, more precisely in the form of an exit face of a plate with an appropriate curvature so that the light emitted from the cell is less than the critical The angle of incidence of the angle of refraction reaches this face in order to pass through it.

Other references such as US 6 091 384 and US 6 229 160 propose light extraction systems applied to LED or OLED type electroluminescent panels.

Contents of the invention

The purpose of the present invention is to propose an alternative extraction solution, no longer based on the refraction of the rays emanating from the cell, but essentially on its reflection.

The invention relates to a luminescent or image display panel comprising a one-dimensional or two-dimensional matrix of organic electroluminescent cells arranged on a substrate and divided into at least rows, characterized in that for each cell or group of cells it comprises an optical A light extraction element, the optical light extraction element itself includes:

- an inlet interface optically coupled to an emitting surface of said cell or cells in said set or substrate, thereby capturing light emitted by said cell;

- an exit interface, the shape of which has a suitable curvature so that light rays emanating from the entrance interface strike said exit interface at this exit interface at an angle of incidence less than the critical angle of refraction, thereby passing through said exit interface; and

- Optionally, the intermediate reflective surface has a suitable curvature, so as to send the light emitted from the inlet interface and hits the intermediate reflective surface to the outlet interface, so that it has less than a critical The angle of incidence is the angle of refraction in order to pass through the exit interface.

In summary, each optical light extraction element of the panel consists of:

- an entrance interface optically coupled to the cells of said plate or to the emitting surface of the substrate so as to capture the light emitted by these cells;

- an exit interface of suitable shape so that the light emitted by the cell passes through the exit interface; and

- Optionally, a reflective surface, modifying the optical path of these rays, thereby reducing the angle of incidence at the exit interface.

In the case of a two-dimensional cell matrix, it is also grouped into columns; thus, one optical extraction element per column is possible.

Preferably, the optical coupling to the unit or to the substrate is provided by an adhesive layer having a refractive index comparable to that of the optical element.

The material of the optical extraction element is transparent; for example, from conventional soda lime glass with a refractive index of 1.52, polymethylmethacrylate with a refractive index of 1.49, or polyethylene terephthalate with a refractive index of 1.57 Choice; since this material has a refractive index higher than that of air and close to that of the electroluminescent layer, the light emitted by the cells of the plate, after passing through the inlet interface of the extraction element, is in a larger solid angle than it would be through the air interface of the same shape , which means that this optic captures a portion of the radiation emitted by the cells that is greater than the radiation that would pass directly through the cells to the air without the optics; thus, the optic greatly increases the level of light extraction.

According to the invention, said optical element is specially designed so that almost all the light rays penetrating the entrance interface are emitted through the exit interface,

- or by modifying the orientation of these rays, in particular by reflection, so that they have an angle of incidence at the exit interface that is less than the critical angle of refraction, especially if this interface is planar and parallel to the surface of the substrate;

- or by adjusting the shape of the exit interface, in particular by giving it a convex shape, so that the angle of incidence of these rays at this interface is smaller than the critical angle of refraction at this interface;

— or by employing both measures at the same time.

The adoption of these measures means that for each optical extraction element, the area of its exit interface is larger than the area of its entrance interface; this structure can increase the distance between the edges of the light-emitting areas of multiple units or pixels, which is particularly advantageous Yes, especially in the case of active matrix boards; will expand on this later.

Preferably, for each extraction element, if there is no reflective surface, or suitably said reflective surface, the exit interface has no planar elements; this is because non-planar curved surfaces are best suited to obtain the highest light extraction levels; if the extraction element With reflective surfaces, the invention thus extends to the case where the exit surface is flat, consistent with most of the examples given below.

In a first group of embodiments of the extraction element, the extraction element forms an array of convex microlenses.

The shape of the convex lens of the exit element is very well adapted to the rays emanating from the entrance interface, with which the angle of incidence is smaller than if the interface were flat and parallel to the substrate of the plate; by reducing the incidence at the interface with air angle, greatly increasing the level of light extraction.

The area of each microlens is larger than the area of the light emitting area or pixel of the panel.

Either one microlens per cell, in which case each microlens has two planes of symmetry, the intersection of which is preferably at the center of the cell, or one microlens per cell row or cell column, in which case , each microlens has a plane of symmetry, preferably at the center of the cell row or cell column.

The subject of the invention is a luminous or image display panel as defined in the claims, wherein the extraction element has a reflective surface; this reflective surface is of such shape that any light rays penetrating the entrance interface of the extraction element pass through the Emitted by the exit interface.

The shape of the exit interface of each optical extraction element may be planar or curved; the shape has a suitable curvature so that light emitted directly from the entrance interface or by one or more reflections on a reflective surface is emitted at the exit interface with Angles of incidence less than the critical angle of refraction impinge on the exit interface, thereby passing through the exit interface.

According to a second set of embodiments of the extraction element, wherein the extraction element has a reflective surface, this surface is preferably of a suitable shape so that any light entering through the entrance interface of the extraction element is emitted through the exit interface; this condition is expressed as "marginal rays "principle, with reference to the book titled "High Collection Nonimaging Optics", Chapter 4, paragraph 2, W.T.Wleford & R.Winston, Academic Press, Inc.1989, page 54; preferably, the reflective surface has at least one plane of symmetry , and each of the two intersections of this surface with a plane perpendicular to this plane of symmetry forms a partial parabola, as described in Chapter 4, paragraph 3 of that work, especially Figure 4.3, where, unlike the present invention, This surface is used as a concentrator; the inlet face of the concentrator described in the work becomes the outlet interface of the extraction element according to the invention, and the outlet face of the concentrator becomes the inlet interface; as in the work As stated in Chapter 4, paragraph 5, each of the two lines of intersection forms a continuous parabolic portion; preferably, the position of the axis and focus of the parabola of each line of intersection and the thickness L of the extraction element are chosen such that the The conditions given in paragraph 3 of chapter 4, in particular, on pages 56-57, so that the "marginal rays" principle is satisfied; in short, each of the two lines of intersection preferably defines A reflective surface consistent with what is defined in this work is called CPC (Compound Parabolic Concentrator).

Since, according to the invention, the optical extraction elements operate by reflection, a considerably high fraction of the light emitted by the cells can be extracted and panels with higher luminous efficiency are obtained.

Other shapes of reflective surfaces may be used without departing from the invention, such as conical or parabolic in which the two lines of intersection described above will have the same axis.

The reflective surfaces thus form reflectors; there may be one reflector per unit, in which case each reflector preferably has two planes of symmetry, usually mutually perpendicular, the intersection of which passes through the center of the unit; Each unit row or unit column has one reflector, in which case each reflector has a single plane of symmetry at the center of the row or column.

The invention also applies to the case where each extraction element has a lens-shaped exit interface and a reflective surface; preferably, this reflective surface is the above-mentioned CPC type surface, which is given in Chapter 5, paragraph 8 of the above-mentioned work An example of a component.

In a variant, the extraction elements are also used to collimate the light; for each extraction element, the exit interface and/or, where appropriate, the reflective surface is of a shape such that the light rays lying at the exit interface lie on a spherical surface strictly smaller than 2π degrees; thus, the shape of the exit interface and/or the shape of the reflective surface is advantageously adapted to limit the light emitted by the plate in the direction of a limited area of space, especially towards the viewer of the image to be displayed ; Therefore, without additional costs, the efficiency of the board is greatly improved.

Preferably, the light extraction elements of the plate constitute a single part forming the extraction layer.

This part then aggregates all lenses or parabolic reflective or other light extraction elements; this structure is particularly advantageous because it is less expensive to manufacture the extraction elements and to assemble them on the board, since in a single operation all extraction The elements are positioned on the cells of the board; moreover, an extraction layer can be used to protect the cells of the board, in particular against their reaction with ambient water and/or oxygen.

If the extraction element is made of plastic, this single part can be produced very cheaply by conventional rate conversion methods such as compression molding or injection molding.

Typically, the cell matrix includes an electroluminescent layer between two electrode array layers, one of which is referred to as the "lower" layer, on the side facing the substrate, and the other, referred to as the "upper" layer , on the other side, each cell is located in the overlapping area between the lower and upper electrodes; the board may include other arrays of electrodes, especially in the case of active matrix boards.

When the upper electrode is transparent or translucent, the plate is then referred to as a "top-emitting" plate; the extraction element is then positioned on top of this upper layer; preferably, according to the first or second set of embodiments, the extraction element constitutes A single part, forming the extraction layer and forming the encapsulation layer sealed relative to the substrate, thereby preventing the intrusion of gases such as oxygen or water vapor into the cell, thereby preventing the electroluminescent layer from being damaged by these gases; the space for encapsulation Adsorbents or desiccants capable of absorbing these gases may be included.

Preferably, this desiccant is placed in pores formed in the thickness direction of the extraction layer, which open towards the interior of the plate in the direction of the electroluminescent layer, and are located between the extraction elements, so that the adsorbent does not hinder the passage of light.

When the underlying electrode is transparent or translucent, the panel is referred to as a "back-emitting" panel; the extraction element is then positioned on the opposite side of the substrate from the underlying layer.

Preferably, at this time, the extraction layer itself forms the substrate of the plate; considering the manufacture of the plate, then, on the extraction layer, on the side of the inlet interface, a plurality of layers, especially electrode layers and layers of electroluminescent material, are arranged, these The layers constitute a two-dimensional matrix of plate cells; thus, the extraction layer is preferably made of glass.

According to a variant of the invention, the substrate has a fibrous structure, the fibers of which are adapted to guide light from one side of said substrate to the other.

The entry interface of each extraction element may cover a cell group, especially a cell row, or if the matrix is two-dimensional, such as a cell column; in this case, each extraction element preferably has an The plane of symmetry at the center of the cell column.

Preferably, each cell of the group emits light of the same primary color; in other words, each group of cells then corresponds to cells emitting light of the same color.

On the other hand, the inlet interface of each extraction element may cover a single cell; in this case, each extraction element preferably has two planes of symmetry, the intersection of which passes through the center of the cell; In the case of a plate, the extracted elements form a two-dimensional array.

In a variant of the invention, the surface density of the extraction elements may be greater than the surface density of the unit pack or plate unit.

In the case of a passive matrix panel, the array electrodes are preferably in the form of parallel conductor strips of constant width; then, preferably, the electroluminescent layer is divided into parallel strips emitting light of different primary colors and arranged in an alternating manner; Then, preferably, each electrode strip of the upper layer is parallel to the strip of the electroluminescent layer and is located in the center of the strip of the electroluminescent layer.

However, the invention is particularly advantageous in the case where the substrate of the panel forms an active matrix; this is because in order to integrate active matrix and electroluminescent panels it is often necessary to limit the area dedicated to the electroluminescence of each cell; in This limitation is no longer a disadvantage when using the light extraction element according to the invention.

Finally, the invention applies in particular to image display panels.

Description of drawings

The invention will be more clearly understood by reading the following description given as a non-limiting example with reference to the accompanying drawings, in which:

- Figures 1 and 2 show back-emitting electroluminescent panels, respectively with and without spacers, before application of a light extraction layer according to the invention;

- Figures 3 and 4 show top-emitting electroluminescent panels, respectively with and without spacers, before the application of the light extraction layer according to the invention;

- Figures 5 to 9 show a top luminescent panel without partitions, in side or cross-sectional views and in rear and front views, with light extraction elements of a first group of embodiments wherein the light extraction elements are in the form of microlenses: Figure 5 shows the general case; Figure 6 shows the case where a graded-index plate is used as the extraction layer; Figures 7 and 8 show the case where long lenses are placed parallel to the rows or columns; and Figure 9 shows The case where the extraction layer is formed by a two-dimensional lens matrix;

- Figure 11 shows in section a back-emitting electroluminescent panel without partitions, with light extraction elements in the form of reflectors according to a second set of embodiments of light extraction elements;

- Figure 10 and Figures 12 to 14 show a top luminous panel without partitions in side or section view and in rear and front views, with light extraction elements in the form of reflectors according to a second set of embodiments: Fig. 10 shows the general case; Figures 12 and 13 show the case where long reflectors are placed parallel to the rows or columns, respectively; and Figure 14 shows the case where the extraction layer is formed by a matrix of two-dimensional reflectors;

- Figures 15 and 16 show cross-sectional views of back-emitting electroluminescent panels, the substrate of which is made of fibers used as light guides for the passage of light, with reflectors and microlenses, respectively; and

- figure 17 shows a top view of an active matrix electroluminescent panel before coating of a light extraction layer.

Detailed ways

In order to simplify the description and to clarify the differences and advantages of the present invention compared with the prior art, the same reference numerals will be used to denote elements performing the same functions.

Thus, a board according to the invention comprises:

- a matrix of two-dimensional organic electroluminescent cells arranged on a substrate and divided into rows or columns; and

- A light extraction element, arranged on each cell or cell row or cell column, forming an extraction layer.

First, the manufacture of a panel that does not include an extraction layer dedicated to the present invention in the case of a passive matrix panel will be described with reference to FIGS. 1 to 4 .

The lower electrode in the form of an array, the electroluminescent layer usually comprising alternating bands emitting light of different colors, and the upper electrode in the form of an array can be successively deposited on the substrate using a variety of conventional methods: for example, photolithography, Vacuum deposition, spin-on deposition and/or inkjet printing.

As can be seen above, a distinction can be made between two types of panels: namely, the more general back-emitting, ie light passes through the substrate and thus the lower electrode, and top-emitting, ie light passes through the upper electrode.

For each of these two types, two types of structures are conventionally possible, namely, structures with a separate spacer between the upper electrode strip and the electroluminescent layer strip, and structures without a separate spacer structures; structures without separate spacers are typically produced by deposition methods using shadow masks.

The advantage of separate spacers is that they provide better electrical isolation between rows or columns of cells; the disadvantage is that they require additional cost.

Thus, four board types will generally be encountered and each will now be described in more detail.

In the case of a backlight panel with spacers, Fig. 1 shows a substrate 100 formed from a glass plate, on which a transparent lower layer based on ITO (Indium Tin Oxide) is deposited and then etched, to form strip-shaped transparent electrodes 101; in the case of an active matrix, a rectangular transparent electrode would be etched instead; next, an electrical isolation layer 102 is deposited, leaving a space or gap for each electroluminescent cell, in this case Next, rectangular in shape; line-shaped separators 105 parallel to the lower electrode 101 and perpendicular to its direction are placed between the gaps or spaces in the isolation layer 102; the production of separators is described in US 5 701 055 (PIONEER) possible method; these spacers are made of an insulating material, preferably, the same material as the isolation layer 102; deposited between the spacers 105 and in each gap or space in the isolation layer 102 is an organic electroluminescent layer Forming the strips 103, the organic electroluminescent layer 103 itself is generally structured in the form of several sublayers comprising, inter alia, an organic hole-injection sublayer, an organic electroluminescent sublayer and an electron-injection sublayer; for deposition These organic sublayers are, for example, employed in a vacuum process; in order to obtain alternating bands of different colors, each color is deposited by masking the inter-spacer regions corresponding to the other colors; next, above the organic electroluminescent bands 103 Usually opaque and preferably reflective electrode strips 104 are deposited; here, too, these strips can be structured in the form of several sublayers, for example a sublayer based on lithium fluoride (LiF) and a sublayer based on aluminum, which provides Reflection effect; in this way, a backlit panel with partitions is obtained.

In the case of a backlight without spacers, Fig. 2 shows a substrate 100 formed by a glass sheet, on which, as before, strip-shaped transparent electrodes 101 are deposited; using a mask or a set of masks - one for each color, depositing strips 103 of the organic electroluminescent layer whose structure and composition are identical to those described above; these strips 103 are parallel, oriented perpendicularly to the lower electrode 101, and arranged so as to cover the rectangular area of the cell ; Next, an electrode strip 104 equivalent to that described above is deposited through a mask with narrower apertures located above the electroluminescent strip 103 ; in this way, a backlight plate without spacers is obtained.

In the case of a top luminous panel with spacers, referring to Figure 3, the process used is the same as already described in the case of a back luminous panel with spacers, where the position of the transparent electrode 101 that now belongs to the upper layer is reversed and that now belongs to the lower layer The location of the opaque electrode 104 .

In the case of a top luminous plate without spacers, referring to FIG. 4 , the process used is the same as already described in the case of a back luminous plate without spacers, in which the position of the transparent electrode 101 now belonging to the upper layer and the present The position of the opaque electrode 104 belonging to the lower layer.

Other conventional processes for obtaining a matrix of two-dimensional organic electroluminescent cells, especially in the case of active matrices, may be used without departing from the invention.

As an example, two sets of light extraction elements will now be described, deposited on each cell or each cell row or cell column:

- Extraction elements of the microlens type 20;

- Extraction elements of the parabolic reflector 30 type.

Figure 5 shows extraction elements in the form of microlenses 20 deposited on a top-emitting electroluminescent plate as described above with reference to Figure 4; Lens 20 includes:

- an entrance interface 21 of aperture _LE , optically coupled to the light-emitting surface of the cell or the row or column of cells, so as to capture the light emitted from the electroluminescent layer 103 through the transparent electrode 101; and

- the exit interface 23 of wider aperture _LS , its shape has suitable curvature, thereby the light that emits from entrance interface 21, as shown by the solid line arrow in the figure, at this exit interface 23, is less than the critical angle of refraction The incident angle hits this exit interface 23 .

Thanks to this lens element 20, the extraction of the light emitted by the cell is greatly improved.

Preferably, the collection of extraction elements forms a single part and forms the extraction layer 200; this extraction layer may be made of a transparent polymer material which can be formed relatively cheaply by compression molding or injection molding; this extraction layer may Bonding to the board is by gluing; an intermediate adhesive layer (not shown) then serves as means for optical coupling with the board.

Figure 6 shows a variant in which the extraction layer 200' has a uniform thickness and contains graded index regions 20' which function in the same way as the optical extraction elements described above.

Figures 7 to 9 show other variants related to the shape of the microlenses of the extraction elements:

- FIG. 7B : each extraction element _20L has a plane of symmetry, serves as a cell row of the plate shown in FIG. 7A and is located in the center of the transparent electrode row 101 of this plate;

- FIG. 8B : each extraction element _20C has a plane of symmetry, serves as a column of cells of the plate shown in FIG. 8A and is located in the center of the column of opaque electrodes 104 of this plate; and

- FIG. 9B : each extraction element _20P has an axis of symmetry located in the center of the unit at the transparent row electrode 101 and opaque column electrode 104 shown in FIG. 9A and substantially for this unit.

These embodiments in which the extraction elements are in the form of microlenses also apply to back-emitting electroluminescent panels without spacers, such as those shown with reference to FIG. 2; the extraction layer 200 is optically coupled to the surface of the substrate 100; since the substrate The thickness of the sheet, usually between 0.3 and 1.5 mm, is larger, or even much larger, than the size or diameter of the cell or pixel, so that the amount of light captured by the extraction layer is smaller than in the case of the previous top-emitting plate; by placing the extraction Layer 200 is used as the substrate, preferably a graded index extraction layer 200' as shown in FIG. 6 is used to avoid this disadvantage.

The thickness of the extraction elements in the form of microlenses or extraction layers is a compromise between the level of light extraction, the level of concentration or alignment required (see below), mechanical strength and the level of protection one wants to provide to the plate.

FIG. 10 depicts an extraction element in the form of a parabolic reflector 30 of the "CPC" type described above, arranged on a top-emitting electroluminescent panel without spacers as shown with reference to FIG. 4 .

At each cell of the panel, or per cell row or cell column, each parabolic reflector 30 includes:

- an entrance interface 31 of aperture _LE , optically coupled to the light-emitting surface of this cell _10R , _10G , _10B or cells in this row or in this column, so as to capture the light emitted by these cells;

- a reflective surface 32 having a suitable curvature to send the rays of light emanating from the entrance interface 31 impinging on said reflective surface towards the exit interface 33 so that at this exit interface there is an angle of incidence smaller than the critical angle of refraction, so that Through this export interface;

- The outlet interface 33 of the wider aperture _LS , in this case in the form of a plane.

The light emitted from the entrance interface 31, as shown by the solid arrow in FIG.

Preferably, the collection of extraction elements constitutes a single piece and forms the extraction layer 300; preferably, this extraction layer is made of a transparent polymer material and is formed by compression molding or injection moulding.

The reflective surface 32 is preferably formed by aluminizing the areas of the surface of this layer that must reflect light; in a variant, this reflection is provided by total reflection.

Optical coupling at the entrance interface is achieved with a transparent adhesive layer having a refractive index close to that of the material; however, by coating the entrance interface 31 of the extraction layer with adhesive, there is an application of the adhesive to the reflective surface 32 This is a hazard, which would be particularly disadvantageous if the reflection was provided by total reflection; aluminizing the reflective surface 32 avoids this disadvantage.

Thanks to this reflector element 30 the extraction of the light emitted by the cells of the panel is greatly improved.

Figure 11 shows a variant in which an extraction layer 300' comprising a reflector 30 identical to the aforementioned reflector is arranged on a back-emitting electroluminescent panel without spacers as previously shown with reference to Figure 2; This variant also differs in that the density of extraction elements is much greater than before - in fact, there are twice the number of extraction elements in cells or columns of cells or even cells; this variant also differs in that it includes setting An array of reflector elements 28 between the substrate 100 and the extraction layer 300', between the inlet interfaces 31 of adjacent extraction elements; this array of reflector elements 28 makes it possible to further increase the extraction efficiency, as shown in the figure The path of the ray is shown.

Figures 12 to 14 show other variants related to the shape of the reflector of the extractor element;

- FIG. 12B : each extraction element _30L has a plane of symmetry, serves as a cell row of the plate shown in FIG. 12A and is located in the center of the transparent electrode row 101 of this plate;

- FIG. 13B : each extraction element _30C has a plane of symmetry, serves as a column of cells of the plate shown in FIG. 13A and is located in the center of the column of opaque electrodes 104 of this plate; and

- Fig. 14B: each extraction element _30P has an axis of symmetry located in the center of the unit at the transparent row electrode 101 and opaque column electrode 104 shown in Fig. 14A and substantially for this unit.

As can be seen above, the two sets of light extraction elements just described can be applied to back-emitting extraction panels, with the disadvantage that the amount of light captured by the extraction layer is smaller than in the case of the former top-emitting panels; one way of avoiding this disadvantage is to use fiber-based A substrate 100'' in the form of a plate (of optical fibers) with fibers 106 normal to the normal plane of the plate and adapted to direct light from one side of the plate to the other along the shortest possible optical path.

15 and 16 show two variants of this embodiment, respectively the case where the extraction layer 300 is formed by the reflector 30 and the case where the extraction layer 200 is formed by the microlens 20 .

The advantage of using an extraction layer in the form of a single part 200, 300 with such a substrate 100" is that it provides a very good seal and a very good protection of the plate unit, since its fiber (optical fiber) based structure will allow It is easily water-permeable and air-permeable, and the substrate alone will not be sufficient protection against water and oxygen; in fact, the organic materials of the electroluminescent layer 103 are known to degrade rapidly under the action of water or oxygen.

In general, the extraction layer can advantageously be used as an encapsulation layer when it is made in a single part, so as to substantially improve the protection of the unit from ambient oxygen or ambient water; this advantage can especially be applied in the case of top-emitting panels, regardless of the extraction element Belonging to the first and/or second group of embodiments.

The invention has been described with reference to organic electroluminescent panels without spacers; it can also be applied to panels with spacers as shown in Figures 1 and 3 above; in the case of top-emitting panels, typically less than The spacer height of 10 μm is not a hindrance for applying the light extraction element to the reflector, which can be kept away from the spacer due to the curvature of the reflector.

Two sets of light extraction elements have been described with reference to exit interface shapes in the form of microlenses for the first set of embodiments and reflective surface shapes in the form of parabolas for the second set of embodiments, but other geometries may also be used. For the first set of exit interfaces and the second set of reflective surfaces, it is preferred to use curved surfaces that are more efficient for extraction, rather than surfaces with flat areas.

In a general variant of the invention, the light extraction means are also adapted to reduce the aperture of the luminous cone of the panel, thereby confining it to the area of space located in front of the panel, in particular for viewing the image to be displayed; according to the well-known The geometry of the outlet interface 23, 33 of the extraction element and/or the geometry of the emission surface 32 is adjusted in such a way as to obtain this converging effect.

It can be seen that, with a light extraction arrangement as described above, each extraction element provides an exit aperture L _S much larger than the emission aperture L _E of the corresponding cell; in the absence of converging effects, the ratio L _S /L _E is preferably approximately 4. When there is convergence effect, the ratio L _S /L _E is greater than 4. Thanks to the invention, it is possible to substantially reduce the actual light-emitting area of the electroluminescent layer in each cell without causing a loss of the total luminous flux in the panel; this is because the increase in the level of light extraction compensates for the increase in the actual light-emitting area of each cell. reduce.

The reduction of the actual light-emitting area per cell is particularly advantageous in the case of active matrix boards, where, at each cell, multiple electronic components for driving the cells are etched on the substrate of the board , and inserted therein; now, these components may be large, resulting in a limitation on the actual light-emitting area per unit; this limitation is no longer a hindrance when employing the light extraction device according to the invention.

Figure 17 shows three adjacent cells 10 _R , 10 _G , 10 _B of an active matrix electroluminescent panel, each of which includes: a lower layer electrode connected to a memory component 304, and a solid transparent or translucent The conductive layer is formed here on the upper single electrode (not shown); although the lower electrodes must be separated from each other, on the contrary, for the upper layer, a single electrode may be sufficient; Defining the light-emitting area of each cell, unlike the case of the passive matrix previously described, is not defined by the intersection between the upper and lower electrodes; advantageously, the lower electrode of each cell of the active matrix panel can be selected , thus corresponding to the inlet interface of the extraction element according to the invention.

The invention is particularly advantageous if a two-dimensional matrix of cells, especially the electroluminescent layer and upper electrodes, is produced by deposition methods using shadow masks or inkjet printing; distance, thus increasing the pattern width of the mask used to deposit multiple sub-layers of the plate; such a mask with a wider pattern is very easy to position; therefore, in its fabrication usually a shadow mask method or inkjet printing The invention is particularly advantageous in the case of a plate of the method without partitions.

The invention also applies in the case of electroluminescent panels whose cells have photoluminescent converter elements, as described, for example, in reference US 51216214; in such panels, the electroluminescent layers of all cells emit light of the same color , for example, blue; arranged in the red and green units above the electroluminescent layer are photoluminescent elements that emit red and green light respectively under excitation of blue light; in variants, a filter layer can be added, Especially for Blu-ray. In the manufacture of such plates it is advantageous to produce photoluminescent elements on the extraction element or extraction layer; for this purpose holes can be formed at the inlet interface of the extraction element and photoluminescent material can be deposited in these holes Middle; Next, as previously described, the extraction element or extraction layer is bonded to the base electroluminescent plate.

Claims (9)

1, a kind of luminous plaque or video display board, comprise that being deposited on substrate (100) goes up also at least by the one dimension or the two-dimensional matrix of the organic electroluminescence cell that divides into groups by row, the matrix of described organic electroluminescence cell comprises the electroluminescence layer between two electrod-array layers, one in two electrod-array layers is called as " lower floor ", be inserted between substrate and the electroluminescence layer, and another is called as transparent or semitransparent electrode " upper strata ", be positioned at a side of the electroluminescence layer relative with " lower floor ", the overlapping region of each organic electroluminescence cell between lower electrode and upper electrode, for each unit or every group of unit when the organic electroluminescent unit is grouped, described luminous plaque or video display board comprise that optics extracts element (20,30), described optics extracts element (20,30) self comprises:

-Entry Interface (21,31) with the emitting surface optical coupled of emitting surface or every group of unit when the organic electroluminescent unit is grouped of described organic electroluminescence cell, thereby is caught the light that is sent by described organic electroluminescence cell;

-outlet interface (23,33); And

-middle reflecting surface (32), has suitable curvature, thereby send light that send from described Entry Interface, the described middle reflecting surface of bump to described outlet interface (23,33), thereby make it have incidence angle at the interface less than the critical refraction angle in described outlet, so that by described outlet interface

It is characterized in that described optics is extracted element to be positioned on this upper strata.

2, luminous plaque according to claim 1 or video display board is characterized in that the described optics of described plate extracts element (30) by single the formation that has formed extract layer (300).

3, luminous plaque according to claim 2 or video display board is characterized in that extract layer forms encapsulated layer.

4,, it is characterized in that described middle reflecting surface (32) does not have the plane surface element according to described luminous plaque of one of aforementioned claim or video display board.

5, luminous plaque according to claim 4 or video display board, the described middle reflecting surface that it is characterized in that each optics extraction element has at least one plane of symmetry, and in the middle of this reflecting surface with form a parabolical part perpendicular to each bar in two intersections on the plane of this plane of symmetry, thereby reflecting surface forms CPC (compound parabolic amplitude transformer) in the middle of making.

6, luminous plaque according to claim 5 or video display board, it is characterized in that when one of described two intersections form the parabolical part of part, select parabolical axle and the position of focus and the thickness L that optics extracts element of every intersection, thereby:

-this focal point F is positioned on the profile that defines described Entry Interface (31);

-this axle is by this focal point F, and by perpendicular to the described plane of the plane of symmetry be positioned at the point of intersection S of this focus with respect to the profile at the described outlet interface (33) of the opposite side of the described plane of symmetry; And

If a ' is the distance of this focal point F and the plane of symmetry, and a is the distance of this S and the plane of symmetry:

-parabolical focal length by f=a ' (1+a '/a) provide; And

The thickness L that-optics extracts element by $L=\left({a+a}^{\′}\right)\sqrt{1-{(a^{\′}/a)}^2}$ Provide.

7, according to described luminous plaque of one of claim 1-3 or video display board, it is characterized in that being divided into group and when each optics extracted Entry Interface (31) the capping unit group of element (30), the central shaft that each optics extraction element (30) has with this element group was the plane of symmetry at center when the organic electroluminescent unit.

8, luminous plaque according to claim 7 or video display board is characterized in that each organic electroluminescence cell of described group sends the light of same primary color.

9, according to described luminous plaque of one of claim 1 to 3 or video display board, it is characterized in that when each optics extracts the single unit of Entry Interface (31) covering of element (30), each optics extracts element (30) and has two planes of symmetry, and the intersection of described two planes of symmetry is by the center of this organic electroluminescence cell.

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